There are no other related applications.
This research was not federally sponsored.
The present invention relates to the production of valuable higher linear olefins from low value butenes via a catalytic disproportionation reaction in a catalytic distillation reactor.
Catalytic disproportionation, transalkylation or metathesis technology refers to the technology, which, in alkenes, exchanges the alkyl groups on both sides of the double bond with another alkene. For example, propylene can be reacted to make ethylene and 2-butene. Typically, the alkene products contain both higher and lower carbon number chains. One of the earlier examples of the prior art is described in the U.S. Pat. No. 3,261,879 (1966) regarding the reaction of propylene mentioned above. This is easily accomplished as the reactions are reversible and proceed to equilibrium, thus if starting with butene and ethylene the reaction will proceed to about 50% conversion to propylene, while starting at propylene, the reaction will proceed to about 50% conversion to ethylene and butene. Most of the prior art describes single reactant phase reactions in a fixed bed, a fluidized bed or a moving bed where the equilibrium limits the conversion to desired alkene. Longer residence times in such systems lead to isomerization and other by-product reactions. U.S. Pat. Nos. 3,463,827 (1969); 3,448,163 (1969); 3,641,189 (1972); 3,676,520 (1972) all describe processes of disproportionation of alkenes where a Group VIB metal carbonyl catalyst associated with alumina or a rhenium heptoxide on alumina, or rhenium heptoxide on alumina with mixtures of other metals. These processes, in part, discuss the reaction of 1-butene to give ethylene and 3-hexene. Although the theoretical conversion of 1-butene to ethylene and 3-hexene is about 50%, none of the references sited above were able to approach even the theoretical conversion with high selectivity to these desired products. Some systems attempted to use high temperature to drive to higher conversion, but with considerable detriment to the selectivity of the reaction because of the increased isomerization rates as well as consecutive reactions of the reaction products.
U.S. Pat. No. 4,709,115 (1987) teaches of improving the selectivity and conversion of the reactions of 1- and 2-butene to ethylene, propylene, 2-pentene and 3-hexene by using a reactive distillation column, which uses rhenium oxide catalyst impregnated on alumina both as a catalyst and a distillation substrate to facilitate phase transfer. In this reactive distillation system the conversion is improved to 85-93% and the combined yield to ethylene and 3-hexene (or ethylene, propylene (light ends) and 2-pentene, 3-hexene (heavy ends) is improved to 79.5-89%. This result is obtained because the light reaction products are removed from the liquid phase immediately and thus push the equilibrium to the heavy products. Also, this invention claims the ability to achieve high reaction rates at moderate (50-130xc2x0 C.) temperatures. However, the products of this reaction are commercially insignificant, because ethylene and propylene are in general less valuable than 1-butene. 2-Pentene and 3-hexene, comprising most of the product weight, do not have valuable commercial outlets. Thus this art does use plentiful and low value feedstocks, but does not make desirable range linear internal olefin products.
U.S. Pat. 5,243,120 (1993) as well as other U.S. Pat. Nos. (3,786,112; 5,043,520; 4,996,386; and 4,180,524) all describe methods of improving yields of medium-range olefins by reacting a high carbon number chain olefin with a low carbon-number chain olefin by affecting simultaneous disproportionation and isomerization of the olefins. Most of the subject matter of these patents refers to the production of detergent-range linear internal (C10-C16) olefins from a feedstock of light (C4-C8) and heavy (C18-C20+) alpha-olefins. Some variation of these processes is a part of current commercial linear alcohols process. These patents advise that physical mixtures of olefin disproportionation catalyst (such as rhenium oxide) and an olefin (double bond) isomerization catalyst (such as potassium on alumina) are able to effectively simultaneously isomerize the double bond initially located in a primary position to a deep internal position and to disproportionate the light olefins with the heavy olefins, thus making a high yield of intermediate olefins Without isomerization, the mixture would tend to make ethylene and very heavy olefin. The process is conducted in a fixed bed reactor. The disadvantage of this process is that it has to use high-value light alpha-olefins and high-value heavy alpha-olefins to produce intermediate olefins of similar value. Thus this art produces some of the high-value higher olefins, but at the expense of consuming other high-value olefins and does not utilize low value feedstocks.
This invention is a process for production of high-value higher olefins from low-value mixed 1- and 2-butene streams via olefin disproportionation in one or in more than one sequential catalytic distillation reactors. The reactor has several catalyst beds in a sequence. The various catalyst beds are: olefin disproportionation catalyst bed, including molybdenum, tungsten, rhenium elements, compounds and mixtures thereof, optionally including cobalt; olefin isomerization catalyst bed, including sodium, potassium, rubidium, cesium elements, compounds and mixtures thereof, and a bed consisting of a physical mixture of olefin disproportionation and olefin isomerization catalysts. The products of this reaction system are ethylene, propylene and some 2-butene (overhead product) and C5-C20 and higher linear internal olefins (bottoms product). This invention improves the art of disproportionation of alkyls by devising a high-yield method of producing a desirably broad range of high-value linear internal olefins from low-value 1- and 2-butenes.